Is there 3-way calling?
Skype conference calls can include up to 25 people, including the host - CPU and network bandwidth are the ultimate determining factors on how many participants are practical
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Call waiting?
while in a call, you are alerted to any incoming call (visually and audibly) and there are many options -- for example you can put the existing call on hold, deal with the new caller and then return to the original caller -- you could also add that caller to the existing call to make a conference call -- etc. etc.
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When over a limit, are you charged? Is the phone service temporarily disabled preventing extra charge? Can the user choose?
when you go over the limit, any SkypeOut call are charged at existing rates (plus a connection fee) so you would need some Skype credit to continue making SkypeOut calls, but no, Skype does not suspend your ability to call or be called
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Can a user disable the recurring monthly subscription charge from the start to decide month-by-month?
you can cancel and re-purchase any subscription at any time without penalty -- unused portion is returned to you in the form of Skype credit
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Does the plan include both calling others as well as receiving calls?
subscriptions are only for calling TO landlines and possibly mobile numbers (depends on sub if mobiles are included, and in case of unlimited US and Canada, mobile numbers ARE included), but you are offered up to a 50% discount on a Skype Online number, which is what non-Skype callers would use when calling from landlines or mobiles -- the idea is that you choose a number which will be a 'local' call (hopefully free) for those callers
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Is 6 hours per day midnight-to-midnight? Is it within any 24-hour period?
it is midnight to midnight, Greenwich Mean Time (GMT) (London time shifts with daylight savings, GMT does not)
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Does it allow calling from any computer where the user can log into Skype?
it matters NOT where you are calling from, only where you are calling TO, so yes, simply sign into any PC that is running Skype and use your subscription
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Can Skype be ran on a flash drive for use elsewhere?
yes, Skype can run from a flash drive, requiring no install on the host computer
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What features are of unlimited use in the subscription service, Unlimited US & Canada?
not quite sure what you are asking, but here goes . . .
subscriptions include Skype voicemail and your use of VM is truly unlimited
outgoing calling is subject to the Fair Use Policy